Centro de Investigación Esquel de Montaña y Estepa Patagónica (CIEMEP), CCT-Patagonia Norte, CONICET-UNPSJB, Roca 780, Esquel, Chubut, 9200, Argentina.
SÖBÖ Geosciences, Ruta 259 km 25, Trevelin, Chubut, 9203, Argentina.
Naturwissenschaften. 2022 Aug 8;109(5):40. doi: 10.1007/s00114-022-01810-z.
Pyrotheria is one of the most peculiar orders of South American native ungulates, whose members evolved from the early? Eocene to the late Oligocene period when they became extinct. Here, we described the most complete specimen of Propyrotherium saxeum ever found, one of the lesser-known representatives of pyrotheres that characterized the middle-late Eocene period of Patagonia (Argentina). It includes a nearly complete mandible and a tusk-like tooth of the same individual, as well as other isolated upper and lower teeth. Propyrotherium saxeum has a dental formula that includes at least P2-M3 and i2?-p3-m3 (lack of p2). It is characterized by some peculiar features of the mandible (e.g., ascending ramus longer than high, hiding the m3 and straight incisura mandibular) and dentition (e.g., cristid obliqua in p3-m3, cristid between posterior lophid and distal cingulid in m1-m3, P3-M3 and p3-m3 bilophodont, P2 and p3-m3 bi-rooted, P3-M3 three-rooted, paraconid in p3). The phylogenetic analysis reveals that Propyrotherium is more closely related to Pyrotherium and Baguatherium, differing from the previous hypothesis, and supports the monophyly of Pyrotheriidae including Carolozittelia, Griphodon, Pyrotherium, Baguatherium, and Propyrotherium. The absolute age obtained through U-Pb zircon dating of the Sarmiento Formation at Cañadón Pelado, the fossil's original locality, indicates that the fossil-bearing tuff would have been deposited between 39.65 and 40.41 Ma, with a weighted mean age of 40.03 ± 0.38 Ma (Bartonian). This implies a biochron much longer than previously thought for Propyrotherium and provides a chronological framework for the fauna of Cañadón Pelado.
Pyrotheria 是南美洲原生有蹄类动物中最奇特的目之一，其成员起源于早始新世到渐新世晚期，后来灭绝。在这里，我们描述了迄今为止发现的最完整的 Propyrotherium saxeum 标本，它是 Pyrotheres 的一个不太为人知的代表，特征是巴塔哥尼亚（阿根廷）中新世晚期。它包括一个近乎完整的下颌骨和一个类似獠牙的牙齿，以及其他孤立的上下牙齿。Propyrotherium saxeum 的牙齿公式至少包括 P2-M3 和 i2?-p3-m3（缺少 p2）。它的特点是下颌骨（例如，上升的分支比高，隐藏了 m3 和直的下颌切迹）和牙齿（例如，p3-m3 中的斜嵴，m1-m3 中的后嵴和远端冠带之间的嵴，P3-M3 和 p3-m3 双尖齿，P2 和 p3-m3 双根，P3-M3 三根管，p3 中的副尖）。系统发育分析表明，Propyrotherium 与 Pyrotherium 和 Baguatherium 的亲缘关系更为密切，与之前的假设不同，支持包括 Carolozittelia、Griphodon、Pyrotherium、Baguatherium 和 Propyrotherium 在内的 Pyrotheriidae 的单系性。通过对 Cañadón Pelado 化石产地的 Sarmiento 组进行 U-Pb 锆石定年，获得了绝对年龄，表明含化石凝灰岩的沉积时间在 39.65 至 40.41 Ma 之间，加权平均值年龄为 40.03 ± 0.38 Ma（巴通期）。这意味着 Propyrotherium 的生物年代比以前认为的要长得多，并为 Cañadón Pelado 的动物群提供了一个时间框架。
